I have disabled the tyre pressure sensors on my Peugeot 407 using Peugeot Planet2000, which is similar to Lexia. From memory, I had to disable the TPS in about 4 or 5 menus. It consisted mainly of changing the menu entry from "Present" to "Absent". Once you change the appropriate entry to "Absent" on the screen, you have to click the "Configuration" button in order to effect the change.
Hope this helps.
